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Motor bearings. The one main area of weakness in naturally aspirated M motors. The S54 motor in the E46 M3 was notorious for bearing issues getting an early reputation as being made out of glass as motors failed left and right. BMW eventually issued a recall and the S54 now is known as one of the greatest M motors ever produced by BMW and having a modern reputation as being very stout taking just about whatever one throws at it.

The S85 V10 did not experience a rash of early failures like the S54 due to the bearings and neither did the S65 V8 in the E9X M3 based on it. However, as the motors reach higher mileage it is becoming clear the motors suffer from unnaturally high rod bearing wear. Why is this? One reason is that the pistons and rods may be a bit too heavy for such a high revving motor (despite BMW's marketing they go with what is cheapest in modern times) causing more wear than normal. The oiling system especially in the S65 V8 is weak so track junkies have been experiencing rod bearing wear issues.

This problem is known in E9X M3 circles with the S65 V8 but it is now coming out with the S85 V10. Why later on the S85? Because the S85 has a slightly different oiling system (BMW went even cheaper on the S65 and this is why a dry sump oiling system is recommended for track guys) and because S85 owners only now are supercharging which puts more stress on the motor. There are more S65 V8's tracking and supercharged so the issue is far more well known with the V8 than with the V10.

For those doubting, here is a picture of BimmerBoost user @CV10T's rod bearings at 91k miles from his S85 V10. Not particularly pretty are they?

So what can one do to prevent premature bearing wear and even worse a motor failure? Well, frequent oil changes are recommended to remove any material in the oil. Secondly, replacing the factory bearings with a set of aftermarket bearings is a good idea. The job is not that bad as @CV10T stated replacing his bearings cost 15 hours of labor plus the cost of the bearings.

BimmerBoost vendor VAC Motorsport has several coated bearing options available including those for the S85 V10 and S65 V8.

Gentlemen, take care of this problem before it's too late especially if you do a lot of spirited driving at high RPM or have a power adder.

Ok dumb question here.... I'm about to get a m3 once my 335 sells...am I crazy? This rod bearing issue is no joke. I guess changing oil every 3500 miles and getting a blackstone report every other change would help?

If a car is running fine at 35-45k miles...isnt it safe to say it's not one of the cars with this issue? I'm looking at used m3's with that milage...

Ok dumb question here.... I'm about to get a m3 once my 335 sells...am I crazy? This rod bearing issue is no joke. I guess changing oil every 3500 miles and getting a blackstone report every other change would help?

If a car is running fine at 35-45k miles...isnt it safe to say it's not one of the cars with this issue? I'm looking at used m3's with that milage...

@bobS, it depends on the year of the car IMO. If it's an early e46 M3 (2001-2002 IIRC), they had issues with the rod bearing becoming misaligned - causing the crankshaft to move out of alignment... BMW had a TSB (or whatever it's called) - and fixed these - and you CAN see if the work has been done, and/or if the engine is one that has the bad bearings.

I haven't heard of many people having issues other than the ones in the above boat. I almost think that the S65 is worse off than the S54 in this regard if the S54 has been repaired.

I guess blackstone reports are good and all, but 3500 mile oil changes is a little much IMO. I go every 5k in my car, and the computer tells me it's fine; however, I am a bit concerned due to the fact that I probably have spent most of the car's life at or above 4k RPM (even at 90 MPH on the highway in 7th gear it's right around 3700) - but so far it's been fine. Once the engine is out of warranty, I will have someone rip it apart and replace the bearings, until then - if it fails, I'll let warranty pick it up. Point is, I wouldn't be as concerned with the previous gen.

@bobS, it depends on the year of the car IMO. If it's an early e46 M3 (2001-2002 IIRC), they had issues with the rod bearing becoming misaligned - causing the crankshaft to move out of alignment... BMW had a TSB (or whatever it's called) - and fixed these - and you CAN see if the work has been done, and/or if the engine is one that has the bad bearings.

I haven't heard of many people having issues other than the ones in the above boat. I almost think that the S65 is worse off than the S54 in this regard if the S54 has been repaired.

I guess blackstone reports are good and all, but 3500 mile oil changes is a little much IMO. I go every 5k in my car, and the computer tells me it's fine; however, I am a bit concerned due to the fact that I probably have spent most of the car's life at or above 4k RPM (even at 90 MPH on the highway in 7th
gear it's right around 3700) - but so far it's been fine. Once the engine is out of
warranty, I will have someone rip it apart and replace the bearings, until then -
if it fails, I'll let warranty pick it up. Point is, I wouldn't be as concerned with
the previous gen.

Well I'm going for a 09-10 m3.... So I guess I'll choose wisely and replace the rod bearings before going FI

Well I'm going for a 09-10 m3.... So I guess I'll choose wisely and replace the rod bearings before going FI

Ahh sorry about that. For some reason I thought I remembered you wanting an e46 before. Talk to VAC - they have solutions for this and have a lot of knowledge. I am sure you will be good. It's a great engine. These things are over reacted to IMO.

Ahh sorry about that. For some reason I thought I remembered you wanting an e46 before. Talk to VAC - they have solutions for this and have a lot of knowledge. I am sure you will be good. It's a great engine. These things are over reacted to IMO.

That's what I'm telling myself too... I plan to hang onto this m3 for a long while. Since it's not my daily I'll only put 3-5k miles a year on it. I also want to go FI..... We'll see

Just built my motor and oem bmw rod bearings for the e46 m3 was bought from the dealer and they came coated. They did not have the color spec I needed and had to get it from Germany. I am not sure if it was a new part number or what but they certainly came coated from the dealer.

I would shy away from changing the specs on the crank when you can get a thicker bearing. This is just my preference

How much longer would that motor have lasted before a bearing change was absolutely necessary?

It was absolutely necessary at this point already.

It would have had severe damage(means damaged crank journals or a rod having the urge to see the daylight) within the next 1-2k.

I just wrote a long essay regarding people wanting to file a complain at BMWNA for that "bearing issue" stuff.
I can copy it and create a new thread over here to discuss,if you want to,Joseph.
Think it might be quite interesting as my point is it is nothing else than engine maintenance like on many other engines the timing belt change at similar mileage for similar cost.

I just wrote a long essay regarding people wanting to file a complain at BMWNA for that "bearing issue" stuff.
I can copy it and create a new thread over here to discuss,if you want to,Joseph.
Think it might be quite interesting as my point is it is nothing else than engine maintenance like on many other engines the timing belt change at similar mileage for similar cost.

I saw two M6 convertibles come in last month both around 50k with this exact issue. Both of them were not owned by enthusiasts. Starting to think the 10w60 is too thick on cold start and causing the issue. It appears that cars that are driven less are more likely to have the issue.

Anyone with a s65 or s85 should be doing blackstone reports at every oil change.